Printing resist, method for preparing the same and patterning method using the same

ABSTRACT

Disclosed herein is a printing resist sequentially transferred to a printing plate and a substrate after being applied to a printing roll. The printing resist comprises at least one polymer main chain bound to a tackiness-inducing vinyl group. The surface of the printing resist has tackiness without complete dryness, thus enabling a correct transfer of the printing resist to the printing plate and substrate.

This is a divisional application of U.S. patent application Ser. No.11/808,418 filed Jun. 8, 2007 now U.S. Pat. No. 7,659,048, which claimsthe benefit of Korean Patent Application No. 2006-52043 filed on Jun. 9,2006, all of which are hereby incorporated by reference for all purposesas if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) device,and more particularly, to a printing resist used as a patterning methodof a liquid crystal display (LCD) device.

2. Discussion of the Related Art

In recent years, a variety of flat panel display devices have beendeveloped that have an ultra-slim display screen with a thickness ofseveral centimeters. In particular, liquid crystal display (LCD) devicesare widely utilized in a variety of applications including notebookcomputers, monitors, spacecraft and aircraft, for example, owing toadvantages such as low operation voltage, low power consumption andportability.

LCDs may include a first substrate and a second substrate, and a crystalliquid layer interposed between the first substrate and the secondsubstrate.

The first substrate may include a plurality of gate lines and aplurality of data lines substantially perpendicular to the gate lines inorder to define pixel regions. The first substrate may also include aplurality of thin film transistors (TFTs) each formed at a crossingbetween an associated one of the gate lines and an associated one of thedata lines, and a plurality of pixel electrodes formed at respectivepixel regions. Each pixel electrode is connected to an associated one ofthe thin film transistors.

The second substrate may also include a blocking layer for blockinglight leakage from the gate lines, the data lines and the thin filmtransistors. The second substrate may also include color filter layersformed on the blocking layer and a common electrode formed on the colorfilter layers.

As mentioned above, the LCD device may include a variety of constituentcomponents. Accordingly, the LCD device is produced through severalprocesses. In particular, photolithography has been generally used topattern each constituent component into various shapes.

FIGS. 1A to 1D are cross-sectional views schematically illustrating arelated art photolithography process.

As shown in FIG. 1A, a pattern layer 20 and a photoresist layer 30 aresequentially formed on a substrate 10.

As shown in FIG. 1B, the photoresist layer 30 is subjected to lightirradiation with a light irradiator through a mask 40 having apredetermined pattern.

As shown in FIG. 1C, the pattern layer 20 and the photoresist layer 30are patterned by developing and etching processes.

As shown in FIG. 1D, the photoresist layer 30 is removed with aphotoresist stripper, to form a final photoresist pattern.

Photolithography necessarily involves a photomask having a predeterminedpattern, that disadvantageously results in an increase in productioncosts. In addition, photolithography involves a developing process,which leads to complex production and consumes a lot of time.

Accordingly, there has been a demand to develop a novel patterningmethod that solves the disadvantages of photolithography. To satisfysuch a demand, a patterning method using a printing roll was suggested.

FIGS. 2A to 2D are sectional views schematically illustrating a relatedart patterning method using a printing roll.

As shown in FIG. 2A, a photoresist 30 is applied to a printing roll 60equipped with a blanket 65 mounted on the surface thereof using aprinting nozzle 50.

Since the blanket 65 mounted on the surface of the printing roll 60 ismade of an elastic resin, it reduces the friction between the printingroll 60 and a printing plate (not shown), when the photoresist 30applied to the printing roll 60 is transferred to the printing plate.

As shown in FIG. 2B, the printing roll 60 is rotated on the printingplate 70, where protrusions 75 are formed in a predetermined pattern, totransfer a partial photoresist 30 b to the protrusions 75. As a result,the printing roll 60 is patterned by the remaining photoresist 30 a.

As shown in FIG. 2C, the printing roll 60 is rotated on a substrate 10where a pattern layer 20 is formed, to transfer the photoresist 30 a tothe substrate 10.

As shown in FIG. 2D, the pattern layer 20 is etched using thephotoresist 30 a as a mask, followed by removing using a photoresiststripper, to form a photoresist pattern.

The photoresist 30 a is used as a mask for etching the pattern layer ina patterning method using a printing roll as well as photolithography.

Since the photoresist characteristics change upon the introduction oflight, the photoresist is applicable to photolithography. However, whenthe photoresist is employed in the patterning method using a printingroll, the solvent constituting the photoresist may permeate into theblanket. As a result, the blanket is swelling, whereby pattern defectsmay occur, thus making it impossible to realize a desired pattern.

Accordingly, there is an increased need to develop a novel resistcapable of being used as a substitute for the photoresist in apatterning method using a printing roll.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a printing resist, amethod for preparing the same, and a patterning method using the samethat substantially obviate one or more problems due to limitations anddisadvantages of the related art.

One advantage of the present invention is to provide a printing resistcapable of being correctly transferred to a printing plate and asubstrate and thus realizing a desired pattern.

Another advantage of the present invention is to provide a patterningmethod using the printing resist.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will become apparent from thedescription or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, aprinting resist comprises: at least one polymer main chain bound to atackiness-inducing vinyl group.

In another aspect, the present invention is directed to a printingresist which may use a copolymer whose main chains are bound to atackiness-inducing vinyl group. For this reason, the surface of theprinting resist may have a tackiness without dryness, thus being readilyadhered to a printing plate and a substrate.

The printing resist may maintain its tackiness without complete drynessalthough a volatile solvent dissolving the printing resist evaporates.As a result, the printing resist can be desirably transferred to theprinting plate and substrate.

The polymer main chain may be cresol.

The cresol may include at least one of meta-cresol and para-cresol.

The printing resist may further include a volatile solvent.

The volatile solvent may be methanol, ethanol, or iso-prophyl alcohol.

The printing resist may further comprise a surfactant, for example,semi-fluorinated surfactant.

In another aspect of the present invention, a method for preparing aprinting resist comprises: mixing one selected from meta-cresol,para-cresol, meta-cresol bound to a vinyl group, and para-cresol boundto a vinyl group, with one selected from the meta-cresol bound to avinyl group, and the para-cresol bound to a vinyl group; and subjectingthe cresol mixture to copolymerization.

The meta-cresol bound to a vinyl group and the para-cresol bound to avinyl group may be synthesized by reacting the meta-cresol and thepara-cresol with butadiene; respectively.

The copolymerization may be carried out by reacting the cresol mixturewith formaldehyde.

In yet another aspect of the present invention, a method for forming apattern comprises: applying the printing resist according to the presentinvention to a printing roll having the surface equipped with a blanket;rotating the printing roll on the printing plate to partially transferthe printing resist to the printing plate; rotating the resultingprinting roll on a substrate, where a pattern layer is formed, totransfer the remaining printing resist to the substrate; subjecting thesubstrate to heat-treatment; etching the pattern layer; and removing theprinting resist from the substrate.

The heat-treatment may be carried out at about 150° C. or higher.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIGS. 1A through and including 1D are cross-sectional viewsschematically illustrating a related art photolithography process;

FIGS. 2A through and including 2D are sectional views schematicallyillustrating a related art patterning process using a printing roll; and

FIGS. 3A through and including 3F are sectional views schematicallyillustrating a patterning method using a printing roll according to thepresent invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

1. Printing Resist First Embodiment

A printing resist according to a first embodiment of the presentinvention is represented by Formula 1 below:

wherein 1≦k1≦10 and 0≦m1≦10.

As can be seen from Formula 1, the printing resist according to thefirst embodiment comprises meta-cresol (m-CH₃C₆H₄OH) bound to a vinylgroup (CH₂═CH—), more specifically, a copolymer of4-(but-3-enyl)-3-methylphenol and meta-cresol.

In Formula 1, k1 and m1 are the number of 4-(but-3-enyl)-3-methylphenoland meta-cresol present in each unit copolymer, respectively. K1 and m1values represent the ratio of 4-(but-3-enyl)-3-methylphenol andmeta-cresol. In Formula 1, k1 is an integer from 1 to 10, and m1 is aninteger from 0 to 10. For example, when k1 is 1 and m1 is zero, theprinting resist is represented by Formula 2 below:

For example, when both k1 and m1 are 1, that is, the ratio of4-(but-3-enyl)-3-methylphenol and meta-cresol is 1:1, the printingresist is represented by Formula 3 below:

In the case where the printing resist comprises exclusively4-(but-3-enyl)-3-methylphenol (Formula 2), all main chains of theprinting resist have a vinyl group. On the other hand, in the case wherethe printing resist comprises 4-(but-3-enyl)-3-methylphenol andmeta-cresol in a ratio of 1:1 (Formula 3), 50% of the main chains of theprinting resist have a vinyl group.

4-(but-3-enyl)-3-methylphenol and meta-cresol need not necessarily bealternatively arranged. That is, the arrangement of4-(but-3-enyl)-3-methylphenol and meta-cresol is varied in each unitcopolymer.

As the number of main chains having a vinyl group increases, thetackiness of the printing resist increases. Accordingly, by control ofthe ratio of 4-(but-3-enyl)-3-methylphenol and meta-cresol, thetackiness can be adjusted to a desired level depending on the type ofthe printing plate used.

Although the structure of a printing resist where4-(but-3-enyl)-3-methylphenol is bounded to meta-cresol is illustratedin Formula 1, in a case where para-cresol is used instead ofmeta-cresol, the desired effects comparable to the meta-cresol can beachieved.

The printing resist, where 4-(but-3-enyl)-3-methylphenol is bounded topara-cresol, is represented by Formula 4 below:

wherein 1≦k5≦10 and 0≦m5≦10.

The definition and range of k5 and m5 in Formula 4 are the same as thoseof k1 and m1 in Formula 1, respectively.

The printing resist according to an embodiment of the present inventionmay further comprise a volatile solvent and a surfactant, in addition tothe cresol bound to a vinyl group.

Any volatile solvent may be used in the present invention withoutparticular limitation, so long as it is capable of favorably dissolvinga printing resist made of the cresol bounded to a vinyl group uponapplying the printing resist to a printing roll, while it causes nodeterioration of the performance of the blanket mounted on the surfaceof the printing roll.

Preferred is the use of a volatile solvent having a low boiling point,preferably, about 100° C. or lower. This is the reason that the volatilesolvent must be evaporated immediately after the printing resist isapplied to a printing roll. Solvents capable of satisfying all of thenoted requirements may include methanol, ethanol and iso-prophylalcohol, for example.

Since a surfactant may be used to secure spreadability of the printingresist which is applied to a printing roll, it necessarily has superiorcompatibility with the blanket mounted on the surface of the printingroll. When taking into consideration the fact that the blanket is mainlymade of polydimethyl siloxane (PDMS) and is superhydrophobic, asemi-fluorinated surfactant is preferred.

Examples of suitable surfactant include CF₃(CF₂)₄(CH₂CH₂O)₁₀ andCF₃(CF₂)₅(CH₂CH₂O)₁₄. The printing resist comprises about 75% or more byweight of the volatile solvent, about 20% or less by weight of thecresol with a vinyl group, and about 5% or less by weight of thesurfactant.

Second Embodiment

A printing resist according to a second embodiment of the presentinvention is represented by Formula 5 below:

wherein 1≦k2≦10, 0≦m2≦10

As can be seen from Formula 5, the printing resist according to thesecond embodiment comprises para-cresol (p-CH₃C₆H₄OH) bound to a vinylgroup (CH₂═CH—), more specifically, a copolymer of3-(but-3-enyl)-4-methylphenol and para-cresol.

In Formula 5, k2 and m2 are the number of 3-(but-3-enyl)-4-methylphenoland para-cresol present in each unit copolymer, respectively. The valuesof k2 and m2 represent the ratio of 3-(but-3-enyl)-4-methylphenol andpara-cresol. In formula 5, k2 is an integer from 1 to 10, and m2 is aninteger from 0 to 10. For example, when k2 is 1 and m2 is zero, theprinting resist is represented by Formula 6 below:

For example, when both k2 and m2 are 1, that is, the ratio of3-(but-3-enyl)-4-methylphenol and para-cresol is 1:1, the printingresist is represented by Formula 7 below:

In the case where the printing resist comprises exclusively3-(but-3-enyl)-4-methylphenol (Formula 6), all main chains of theprinting resist have a vinyl group. On the other hand, in the case wherethe printing resist comprises 3-(but-3-enyl)-4-methylphenol andpara-cresol in a ratio of 1:1 (Formula 7), 50% of the main chains of theprinting resist have a vinyl group.

Similarly, as in the first embodiment, by controlling the ratio of3-(but-3-enyl)-4-methylphenol and para-cresol, the tackiness can beadjusted to a desired level depending on the type of the printing plateused, and the arrangement of 3-(but-3-enyl)-4-methylphenol andpara-cresol may be varied in each unit copolymer.

Although the structure of a printing resist where3-(but-3-enyl)-4-methylphenol is bounded to para-cresol is illustratedin Formula 5, in a case where meta-cresol is used instead of thepara-cresol, the desired effects comparable to the para-cresol can beachieved.

Preferably, the printing resist, where 3-(but-3-enyl)-4-methylphenol isbounded to meta-cresol, is represented by Formula 8 below:

wherein 1≦k4≦10 and 0≦m4≦10.

The definition and range of k4 and m4 in Formula 8 are the same as thoseof k2 and m2 in Formula 5, respectively.

Similar to the first embodiment, the printing resist according to thesecond embodiment of the present invention may further comprise avolatile solvent and a surfactant, in addition to the cresol bound to avinyl group.

Third Embodiment

A printing resist according to a third embodiment of the presentinvention is represented by Formula 9 below:

wherein 1≦k3≦10 and 1≦m3≦10.

As can be seen from Formula 9, the printing resist according to thethird embodiment comprises meta-cresol bound to a vinyl group (CH₂═CH—),more specifically, a copolymer of 4-(but-3-enyl)-3-methylphenol andpara-cresol bound to a vinyl group (CH₂═CH—), still more specifically, acopolymer of 4-(but-3-enyl)-3-methylphenol and3-(but-3-enyl)-4-methylphenol.

In Formula 9, k3 and m3 are the number of 4-(but-3-enyl)-3-methylphenoland 3-(but-3-enyl)-4-methylphenol present in each unit copolymer,respectively. The values of k3 and m3 represent the ratio of4-(but-3-enyl)-3-methylphenol and 3-(but-3-enyl)-4-methylphenol. Informula 9, k3 is an integer from 1 to 10, and m2 is an integer from 1 to10.

For example, when both k2 and m2 are 1, that is, the ratio of4-(but-3-enyl)-3-methylphenol and 3-(but-3-enyl)-4-methylphenol is 1:1,the printing resist is represented by Formula 10 below:

As shown in Formula 10, in the case where the printing resist comprises4-(but-3-enyl)-3-methylphenol and 3-(but-3-enyl)-4-methylphenol, allmain chains of the printing resist have a vinyl group.

Similarly, in the afore-mentioned embodiments,4-(but-3-enyl)-3-methylphenol and 3-(but-3-enyl)-4-methylphenol need notnecessarily be alternatively arranged.

Similar to the afore-mentioned embodiments, the printing resistaccording to the third embodiment of the present invention may furthercomprise a volatile solvent and a surfactant.

2. Preparation of Printing Resist

Hereinafter, a method for preparing the printing resist according to oneembodiment of the present invention will be illustrated.

First, meta-cresol or para-cresol is reacted with butadiene, asrepresented by Reaction Schemes 1 and 2 below:

As shown in Reaction Scheme 1, meta-cresol (m-CH₃C₆H₄OH) is reacted withbutadiene (C₄H₆) to form 4-(but-3-enyl)-3-methylphenol.

As shown in Reaction Scheme 2, para-cresol (p-CH₃C₆H₄OH) is reacted withbutadiene (C₄H₆) to form 3-(but-3-enyl)-4-methylphenol.

Then, one selected from meta-cresol and para-cresol is mixed with oneselected from 4-(but-3-enyl)-3-methylphenol and3-(but-3-enyl)-4-methylphenol. The mixture is reacted with formaldehydeto prepare a copolymer.

The mixed ratio may be varied depending on the materials of the printingplate and blanket used.

When the amount of 4-(but-3-enyl)-3-methylphenol or3-(but-3-enyl)-4-methylphenol is larger than that of meta- orpara-cresol which contains no vinyl group, a printing resist preparedfrom the mixture has a relatively strong tackiness due to an increase inthe number of the vinyl group bounded to the main chains thereof. On theother hand, when the amount of 4-(but-3-enyl)-3-methylphenol or3-(but-3-enyl)-4-methylphenol is smaller than that of meta- orpara-cresol which contains no vinyl group, a printing resist preparedfrom the mixture has a weak tackiness.

3. Patterning Method Using Printing Resist

FIGS. 3A to 3F are sectional views schematically illustrating apatterning method using a printing roll according to the presentinvention.

As shown in FIG. 3A, a printing resist 300 is applied to a printing roll600 equipped with a blanket 650 mounted on the surface thereof using aprinting nozzle 500.

As shown in FIG. 3B, the printing roll 600 is rotated on the printingplate 700, where protrusions 750 are formed in a predetermined pattern,to transfer a partial printing resist 300 b to the protrusions 750. As aresult, the printing roll 600 is patterned by the remaining printingresist 300 a.

As shown in FIG. 3C, the printing roll 600 is rotated on a substrate 100where a pattern layer 200 is formed, to transfer the printing resist 300a to the substrate 100.

As shown in FIG. 3D, the resulting substrate 100 is subjected toheating. As a result, the double bond of the vinyl group, which is boundto the main chain of the printing resist 300 a, is broken, thus theprinting resist 300 a loses its tackiness. The heating is preferablycarried out at 150° C. or higher.

As shown in FIG. 3E, the pattern layer 200 is etched using the printingresist 300 a as a mask.

As shown in FIG. 3F, the printing resist 300 a is removed using aprinting resist stripper, to form a pattern.

As apparent from the foregoing, according to the present invention,since the printing resist has a polymer main chain bound to a vinylgroup, the surface of the printing resist maintains its tackinesswithout dryness although a volatile solvent evaporates. As a result, theprinting resist can be desirably transferred to the printing plate andsubstrate, and thus a high-quality pattern can be formed.

In addition, the printing resist of the present invention does notaffect a blanket mounted on the surface of the printing roll, thuscontributing to a reduction in replacement costs of the blanket.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method for preparing a printing resist comprising at least onepolymer main chain bound to a tackiness-inducing vinyl group comprising:mixing one selected from the group consisting of meta-cresol,para-cresol, meta-cresol bound to a vinyl group, and para-cresol boundto a vinyl group, with one selected from the group consisting of themeta-cresol bound to a vinyl group, and the para-cresol bound to a vinylgroup to form a cresol mixture; and carrying out copolymerization byreacting the cresol mixture with formaldehyde to form the printingresist, wherein the polymer main chain comprises the meta-cresol or thepara-cresol or the meta-cresol and the para-cresol; wherein the printingresist comprising the meta-cresol as the polymer main chain isrepresented by formula 1 below, the printing resist comprising thepara-cresol as the polymer main chain is represented by formula 2 below,and the printing resist comprising the meta-cresol and the para-cresolas the polymer main chain is represented by formulae 3 to 5 below:

 wherein 1≦k1≦10 and 0≦m1≦10 (1);

 wherein 1≦k2≦10 and 0≦m2≦10 (2);

 wherein 1≦k3≦10 and 1≦m3≦10 (3);

 wherein 1≦k4≦10 and 1≦m4≦10 (4); ;and

 wherein 1≦k5≦10 and 1≦m5≦10 (5).
 2. The method according to claim 1,wherein the meta-cresol bound to a vinyl group is synthesized byreacting the meta-cresol with butadiene, and the para-cresol bound to avinyl group is synthesized by reacting the para-cresol with butadiene.3. A method for forming a pattern comprising: applying a printing resistto a printing roll having a surface equipped with a blanket; rotatingthe printing roll on a printing plate to partially transfer the printingresist to the printing plate; rotating the resulting printing roll on asubstrate, where a pattern layer is formed, to transfer the remainingprinting resist to the substrate; subjecting the substrate toheat-treatment; etching the pattern layer; and removing the printingresist form the substrate wherein the printing resist comprises at leastone polymer main chain bound to a tackiness-inducing vinyl group,wherein the polymer main chain comprises the meta-cresol or thepara-cresol or the meta-cresol and the para-cresol; wherein the printingresist comprising the meta-cresol as the polymer main chain isrepresented by formula 6 below, the printing resist comprising thepara-cresol as the polymer main chain is represented by formula 7 below,and the printing resist comprising the meta-cresol and the para-cresolas the polymer main chain is represented by formulae 8 to 10 below:

 wherein 1≦k1≦10 and 0≦m1≦10 (6);

 wherein 1≦k2≦10 and 0≦m2≦10 (7);

 wherein 1≦k3≦10 and 1≦m3≦10 (8);

 wherein 1≦k4≦10 and 1≦m4≦10 (9) ; and

 wherein 1≦k5≦10 and 1≦m5≦10 (10).
 4. The method according to claim 3,wherein the blanket is made of polydimethyl siloxane (PDMS).
 5. Themethod according to claim 3, wherein the heat-treatment is carried outat 150° C. or higher.